From 030fe31760169783537162b83af89e551bf120f6 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Fri, 11 Dec 2020 16:48:47 +0100 Subject: libbb: make msleep() result in only one syscall instead of looping function old new delta msleep 45 52 +7 Signed-off-by: Denys Vlasenko --- libbb/bb_do_delay.c | 18 ++++++++++++++++++ libbb/platform.c | 1 - 2 files changed, 18 insertions(+), 1 deletion(-) (limited to 'libbb') diff --git a/libbb/bb_do_delay.c b/libbb/bb_do_delay.c index 3dbf032db..9a84fa24b 100644 --- a/libbb/bb_do_delay.c +++ b/libbb/bb_do_delay.c @@ -36,6 +36,7 @@ void FAST_FUNC sleep1(void) void FAST_FUNC msleep(unsigned ms) { +#if 0 /* 1. usleep(n) is not guaranteed by standards to accept n >= 1000000 * 2. multiplication in usleep(ms * 1000) can overflow if ms > 4294967 * (sleep of ~71.5 minutes) @@ -46,4 +47,21 @@ void FAST_FUNC msleep(unsigned ms) ms -= 500; } usleep(ms * 1000); +#else +//usleep is often implemented as a call to nanosleep. +//Simply do the same to implement msleep. +//it's marginally larger, but wakes your CPU less often: +//function old new delta +//msleep 45 52 +7 + struct timespec ts; + ts.tv_sec = ms / 1000; + ts.tv_nsec = (ms % 1000) * 1000000; + /* + * If a signal has non-default handler, nanosleep returns early. + * Our version of msleep doesn't return early + * if interrupted by such signals: + */ + while (nanosleep(&ts, &ts) != 0) + continue; +#endif } diff --git a/libbb/platform.c b/libbb/platform.c index d2b263a6d..329b0237e 100644 --- a/libbb/platform.c +++ b/libbb/platform.c @@ -27,7 +27,6 @@ int FAST_FUNC usleep(unsigned usec) * If a signal has non-default handler, nanosleep returns early. * Our version of usleep doesn't return early * if interrupted by such signals: - * */ while (nanosleep(&ts, &ts) != 0) continue; -- cgit v1.2.3